Microwave hybrid junction



Patented Nov. 20, 1951 MICROWAVE HYBRID JUNCTION Harald T. Friis, Rumson, Willard D. Lewis, Little Silver, and Le Roy 0. Tillotson, Holmdel, N. J assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 5, 1947, Serial No. 789,850 I This invention relates to an improved type of wave guide junction and to an improved wave guide hybrid structure employing the improved type of junction.

Objects of the invention are to provide types of wave guide junctions and wave guide hybrid structures which will have improved electrical impedance characteristics and convenient mechanical structures.

Other and further objects will become apparent during the course of the following description and from the appended claims.

The devices of this invention were especially designed for use as component elements of the hybrid branching filters disclosed and claimed in the copending sole application of W. D. Lewis, Serial No. 789,985, filed December 5, 1947, and assigned to applicants assignee. This application became United States Patent 2,531,447, granted November 28, 1950.

In accordance with the principles of the invention, the Wave guide junction can be more readily understood, if it be considered to be two short sections of identical rectangular wave guide, brought together at an angle of approximately 20 degrees to form an E-plane junction of V shape with the exterior or base apex of the V truncated.

In many practical applications employing wave guide transmission lines, a wave guide of rectangular cross-sectionis employed in which one cross-sectional dimension is greater than the other. With such structures it is the usual practice to employ fundamental mode TE1,o waves, as defined by S. A. Schelkunoff in his book entitled Electromagnetic Waves, pages 386 to 395, inclusive, with the electric vector parallel with the shorter cross-sectional dimension of the guide. The shorter cross-sectional dimension of the guide is accordingly known as the E-plane dimension and the longer cross-sectional dimension as the H-plane dimension. As employed by those skilled in the art, the terms E-plane and H-plane have collective connotations and include all longitudinal planes within the guide which are parallel with the electric andmagnetic vectors, respectively. These connotations follow naturally from the fact that the 'IEm mode wave extends completely across the cross-section of the guide. All planes within the guide parallel with the shorter sides will therefore include an electric vector of the wave. Likewise all planes parallel with the longer sides will include 'a magnetic vector of the wave. Alternatively, wave guides of square cross-section can be used in 5 Claims. (Cl. 178-44) which case the E and I-I-plane dimensions are identical in length. With a wave guide of square cross-section, the TE1,0 mode wave can be, as is" well known to those skilled in the art, introduced into the guide with the electric vector parallel to either pair of opposing sides, so that one can arbitrarily designate either cross-sectional dimension as the E-plane dimension, whereupon the other cross-sectional dimension becomes, of

necessity, the I-I-plane dimension. In CQIlIlBO-f tion with wave-guidejunctions of the present invention, they are referred to as E-plane junctions because, as is apparent from Figs. 1 to 3, inclusive, of the drawing, the common plane in which the longitudinal axes of the wave-guide sections, forming the junction, lie, is parallel with the direction of the electric vector of a 'I'E1,0 wave propagated in the usual manner through these wave-guide sections, i. e. with the electric vector parallel to the shorter sides of the guide. Should wave-guide sections of square cross-section be employed in a wave-guide junction of the invention it will, of course, function as intended only if the electric vectors of the 1 Waves in the sections of the junction are parallel with the plane containing the longitudinal axes of both wave-guide arms. I

The inner sides of the arm portions of the E planewave-guide junction of the invention form *the interior apex of the V-shaped structure and terminate at the line of intersection of said inner sides, at which point the structure is, of

course, substantially twice as wide as theiE- a plane dimension of one of the wave guides.

truncated base, along the longitudinal axis to the line of intersection of the inner sides of the arms of the structure, is substantially one-halt wavelength of the lowest frequency of the frequency range to be transmitted through the structure. The portion of the structure included between the truncated base and a plane parallel to the plane of the truncated base, the parallel plane including the line of intersection ofthe inner sidesof the two arms of the structure is defined for the purposes of this application as or throat of the wave-guide,

the throat section junction.

The outstanding features of this type 01' guide junction arethe smooth transitionwfrom wave apropos The end of member 408 nearer the coaxial coupling is closed, as shown clearly in Fig. 2, and the coaxial coupling member is centered horizontally in member 406 at a distance of approximately an eighth wavelength from the closed end of member 408.

Bymeans of a housing member 422 affixed to member 400 and a bushing 420 affixed to memher 406 the latter can be rotated about the vertical center line of member 5 and can be fixed at any angle by tightening set screw 418, which registers with a small groove in the side of bushmg 420.

The open end of memberswt is provided with a'flange 408 to facilitate coupling to another wave guide transmission line, or to a terminating device of suitable impedance.

The internal dimensions of member 406 are preferably those of the wave guidesto which 2.290 inches (Ii-plane) and 1.145 inches (E5- plane).

6 This means that with the other three arms properly terminated, energy introduced into any one of the four terminations will not appear in its conjugately related termination but will divide equally between the, other two terminations. If the input termination P is used, since it has eflectively a paralle connection with the two output terminations A and B, the portions (halves) of the total input voltage wave energy transmitted to A and B will travel away from,

the junction in phase. If the input termination S, is used, since it has effectively a series",

connection, the portions (halves) of the total inputpower or voltage wave energy in the two.

output terminations will be precisely opposed in phase. In each instance, reciprocal relations exist, i. e. if equal powers (voltage wave energies) are introduced in phase into terminations A and B of the junction, the voltage wave energies will combine inthe one of the other pair of terminations (i. e. P and S) which has effectively a parallel connection (i. e. termina tion P) with the terminations A and B. If

The member 4|! can obviously be simply a hollow or open V-shaped member and the coaxial coupler can be constructed in the usual;

Minor impedance irregularities can be eliminated by inserting small pins 60! to 608, inclusive, in the sides of member 400 spaced along the center line of their respective sides by approximately one-eighth wavelength of the median frequency of the frequency range employed. In many instances these can be omitted and in most cases only four, such as GM to 604, inclusive, near the smaller end of member 400 will be found entirely sumcient. These pins introduce impedance irregularities of such character as to compensate for those introduced by other apparatus to which the junctionis connected when in use. (For example the filters of the above mentioned Lewis application.)

Member 4"; extends into member 400 approximately .4 wavelength from the right. end of bushing M4, and being positioned along the longitudinal axis of member 400, as shown, it constitutes a paralle coupling to the two arms A and B of the truncated V-shaped member 400. Alternativelythe coupling conductor comprising the portion of member 6 extending to.

the right of bushing 4 can be supported by a vertical rod, the rod being parallel with the E- plane of the wave guide junction and connecting at its upper end to a short section of coaxial line coupling. To preserve the symmetry of the arrangement the coupling conductor H6 or its equivalent should be situated along the longitudinal axis of the throat portion of the wave guide junction.

Because of the symmetry of the arrangement, the coupling afforded by member 4| it and the associated coaxial coupling members described in detail above, is conjugate with respect to the "series coupling which the opening at the small end S of member 400 affords to the two arms A and B of the larger end of member 400.

To summarize, the device illustrated in Figs. 1, .2 and 3 is a "hybrid" microwave junction device in which the terminations A and B (Fig. 3) are "'conjugately related and terminations S and P (Fig. 3) are also conjugately related.

given in the above-mentioned copendmg applicaequal powers (voltage wave energies) are introduced out of phase into the pair of conjugate terminations A and B, the powers will combine in the termination of the other pair which has effectively a series connection (1. e. termination S) with the terminations A and B.

A number of other arrangements within the spirit and scope of the invention will readilyoccur to those skilled in the art. A more detailed discussion of the properties of hybrid junctions and illustrations of their utility are tion of W. D. Lewis. The scope of is defined in the following claims.

What is claimed is: i

1. An E-plane wave guide junction for use in the transmission of high frequency electromagnetic wave energy of the TE1,0 fundamental mode, said junction being adapted to join three like wave guides of rectangular cross section, having predetermined E-plane and H-plane dimensions, said junction comprising a V-shaped structure having a throat section and two like arms symmetrically joined to said throat section, the interior or base apex of the V being truncated, said structure being formed by upper and lower truncated V-shaped parallel plane surfaces separated by the H-plane dimension of said wave guides, said upper and lower surfaces being joined by four plane side surfaces perpendicular to said upper and lower surfaces, respectively, two of said side surfaces enclosing the throat portion and forming the outer sides of the two arms respectively, the remaining two of said side surfaces forming the inner sides of the two arms, respectively, and joining each other at the junction plane between said throat portion and said arms, the side surfaces at the truncated end of said V structure and throughout the length. of the arms of the V structure being spaced apart by the E-plane dimension of said wave guides, the said truncated end of said V structure and the free ends of the arms of the V structure being open and adapted to be connected to said wave guides, respectively, the distance from the truncated end of said structure to the surface at which said arms. join the throat portion of said V structure being at least one-half wavelength the invention of the lowest frequency to be transmitted through said wave guides. V

2. A microwave hybrid junction comprising the qilane'fdimfehsion marine section'and'two like having armssym inetrio'ally 'joiried tdsai'd throat"'sebtionfsaidj unction c'om'prisifig pper "and" lower" plane parallel truncated V-shaifidisurfaoes 'spac'ied apart by the H=p1ane dimension or the ave guides tobe' jO iIi'edfthe sid'eyof thejflnotibnj being plane surfaces perpendicularly positioned" with re'sbe'ctto said "upper" and lower surfaces" and" joining the ''outer" longitudinally extending V edges of said ufiiar andlowr sur-face'sj'saidside' surfaces being" inclined at equal angles" with respect to th'edongitudinal axis "of the junctionlithe truncated end or 'ithe' v 'being' open fand having" c'ross'=sctionaidimensions identicatwith those of :saidwave guides; thear'ms'of the junction-'having-- unif 01 m eross se'ctional dimensions "identical with those oi s'aid wave guides the 'inn'er'sides of 7 said arms being planegsurfaces perpendicularly positioned with respect to sailiiupper and lower surfaces and joining the inner longitudinally extending edgesof said upper and lower surfaces, said inner sides of said arms joining andtermihating at a trans verse line normal to the V-,,

shaped sides of the junction at a point on the longitudinal center line of said structure at whichi v the; distance between the inclined outer side sur-r faces oi the junction are separated by a distance equal to twice the E-plane' dimension of said wave guides the distance from said last-men tioned point vand the truncated end of the junction being substantially one-half wavelength of the lowest frequency to be transmitted through said junction. v V

mission of. high frequen'cy electromagnetic wave W e id s-q eenon; aving predetermined 116,110 Australia;

"wave guide junction for use in the trans-Z n j the f theirflong'itu' "plane; said terminating fa ii surface sai mr'oat portio'ngf v H; v

Date

r A pr," 11,"1942 1 ".QI IRE RE QE I 3 Tyrrell, ifWave Guide Bridge Circuits pub-:.

lished ingl. RmEt Pltqcfiedings; November; 1947,

pages 1294',1306 inclusive. 

